For detecting spatial surroundings, so-called 3D laser scanners are typically used. These are set up at a location and scan a 3D scenario starting from this location. Here, the measuring procedure requires rotations about two orthogonal axes, namely about a vertical axis and a horizontal axis rotating about the vertical axis. The rotation about the vertical axis is effected by the movement of the rotor around the stator, the second axis of rotation being present in the rotor.
In embodiments according to EP 1 562 055, the entire transmitting and receiving optical system is arranged in a fixed manner. A deflecting mirror which is mounted on the rotor so as to be rotatable about a horizontal axis is arranged perpendicularly above the transmitting and receiving optical system. The laser light is fed via the transmitting optical system onto the deflecting mirror. The potential uses of these embodiments are greatly limited owing to the limited detection range. What is also critical in the case of this design is the relatively large dimensions and the variability of the optical beam path via the adjustment of the mirror, which makes efficient suppression of scattered light from the collimated transmitted beam considerably more difficult. Since practically only non-cooperative surfaces having relatively poor reflectivity and strong scattering (low albedo) are surveyed over large distances in the surveying of arbitrary 3D scenarios, the adverse effect of scattered light should not be underestimated and rapidly reaches the order of magnitude of the signal to be measured.
A further disadvantage is the openness of the optical structure since the mirror must be freely moveable within the optical structure. Covering of the system for protection from dust and other environmental influences is therefore necessary on the one hand but on the other hand once again generates the described scattered light problem at the beam exit.
The document DE 295 18 708 U1 describes a theodolite having a telescope which is rotatable about a vertical axis and pivotable about a horizontal axis. The theodolite also comprises a laser distance-measuring apparatus, the laser beam for the distance measurement being introduced into the beam path of the telescope of the theodolite. For this purpose, the laser source is firmly connected in the tilt axis of the theodolite to the telescope and the laser beam is reflected into the sighting axis of the beam path of the telescope by at least one deflecting element. For determining the distance values, evaluation electronics are arranged on the telescope.
The evaluation electronics lead to an increase in the size of the telescope, the telescope for a 3D laser scanner itself requiring too much space and meaning additional mass. A further disadvantage of the evaluation electronics on the telescope is that the evaluation electronics must be connected via electrical supply cables and via signal lines through the pivot axis of the telescope. If the telescope is to be freely rotatable about the horizontal axis, the electrical supply of the laser source must be effected via a rotary lead-through. The known electrical rotary lead-throughs are complicated and susceptible to faults when the device is used under tough conditions.